PowerPC PLT stub alignment fixes

[Alan Modra <amodra at gmail dot com>]

Asking for ppc32 plt call stubs to be aligned at 32 byte boundaries
didn't quite work.  For ld.bfd they were spaced 32 bytes apart, but
only started on a 16 byte boundary.  ld.gold also didn't get it right.

Finding that bug made me check over the ppc64 plt stub alignment,
where I found that negative values for alignment (meaning align to
minimize boundary crossing) were not accepted.  Since no one has
complained about that, I guess I could have removed the feature from
ld.bfd documentation, but I've opted instead to correct the code.

I've also added an optional alignment paramenter for ppc32
--plt-align, for some consistency with gold and ppc64 ld.bfd.

bfd/
	* elf32-ppc.c (ppc_elf_create_glink): Correct alignment of .glink.
	* elf64-ppc.c (ppc64_elf_size_stubs): Handle negative plt_stub_align.
	(ppc64_elf_build_stubs): Likewise.
gold/
	* powerpc.cc (param_plt_align): New function supplying default
	--plt-align values.  Use it..
	(Stub_table::plt_call_align): ..here, and..
	(Output_data_glink::global_entry_align): ..here.
	(Stub_table::stub_align): Correct 32-bit minimum alignment.
ld/
	* emultempl/ppc32elf.em: Support optional --plt-align arg.
	* emultempl/ppc64elf.em: Support negative --plt-align arg.

diff --git a/bfd/elf32-ppc.c b/bfd/elf32-ppc.c
index 73701d4..32104a1 100644
--- a/bfd/elf32-ppc.c
+++ b/bfd/elf32-ppc.c
@@ -3475,14 +3475,17 @@ ppc_elf_create_glink (bfd *abfd, struct bfd_link_info *info)
   struct ppc_elf_link_hash_table *htab = ppc_elf_hash_table (info);
   asection *s;
   flagword flags;
+  int p2align;
 
   flags = (SEC_ALLOC | SEC_LOAD | SEC_CODE | SEC_READONLY | SEC_HAS_CONTENTS
 	   | SEC_IN_MEMORY | SEC_LINKER_CREATED);
   s = bfd_make_section_anyway_with_flags (abfd, ".glink", flags);
   htab->glink = s;
+  p2align = htab->params->ppc476_workaround ? 6 : 4;
+  if (p2align < htab->params->plt_stub_align)
+    p2align = htab->params->plt_stub_align;
   if (s == NULL
-      || !bfd_set_section_alignment (abfd, s,
-				     htab->params->ppc476_workaround ? 6 : 4))
+      || !bfd_set_section_alignment (abfd, s, p2align))
     return FALSE;
 
   if (!info->no_ld_generated_unwind_info)
diff --git a/bfd/elf64-ppc.c b/bfd/elf64-ppc.c
index 65cf7fe..b2d288b 100644
--- a/bfd/elf64-ppc.c
+++ b/bfd/elf64-ppc.c
@@ -12743,9 +12743,11 @@ ppc64_elf_size_stubs (struct bfd_link_info *info)
       if (htab->params->plt_stub_align != 0)
 	for (group = htab->group; group != NULL; group = group->next)
 	  if (group->stub_sec != NULL)
-	    group->stub_sec->size = ((group->stub_sec->size
-				      + (1 << htab->params->plt_stub_align) - 1)
-				     & -(1 << htab->params->plt_stub_align));
+	    {
+	      int align = abs (htab->params->plt_stub_align);
+	      group->stub_sec->size
+		= (group->stub_sec->size + (1 << align) - 1) & -(1 << align);
+	    }
 
       for (group = htab->group; group != NULL; group = group->next)
 	if (group->stub_sec != NULL
@@ -13285,9 +13287,10 @@ ppc64_elf_build_stubs (struct bfd_link_info *info,
   if (htab->params->plt_stub_align != 0)
     for (group = htab->group; group != NULL; group = group->next)
       if ((stub_sec = group->stub_sec) != NULL)
-	stub_sec->size = ((stub_sec->size
-			   + (1 << htab->params->plt_stub_align) - 1)
-			  & -(1 << htab->params->plt_stub_align));
+	{
+	  int align = abs (htab->params->plt_stub_align);
+	  stub_sec->size = (stub_sec->size + (1 << align) - 1) & -(1 << align);
+	}
 
   for (group = htab->group; group != NULL; group = group->next)
     if ((stub_sec = group->stub_sec) != NULL)
diff --git a/gold/powerpc.cc b/gold/powerpc.cc
index 6b65792..3c38a06 100644
--- a/gold/powerpc.cc
+++ b/gold/powerpc.cc
@@ -4186,6 +4186,15 @@ output_bctr(unsigned char* p)
   return p;
 }
 
+template<int size>
+static inline unsigned int
+param_plt_align()
+{
+  if (!parameters->options().user_set_plt_align())
+    return size == 64 ? 32 : 8;
+  return 1 << parameters->options().plt_align();
+}
+
 // Stub_table holds information about plt and long branch stubs.
 // Stubs are built in an area following some input section determined
 // by group_sections().  This input section is converted to a relaxed
@@ -4412,9 +4421,7 @@ class Stub_table : public Output_relaxed_input_section
   unsigned int
   stub_align() const
   {
-    unsigned int min_align = 4;
-    if (!parameters->options().user_set_plt_align())
-      return size == 64 ? 32 : min_align;
+    unsigned int min_align = size == 64 ? 32 : 16;
     unsigned int user_align = 1 << parameters->options().plt_align();
     return std::max(user_align, min_align);
   }
@@ -4483,7 +4490,7 @@ class Stub_table : public Output_relaxed_input_section
   unsigned int
   plt_call_align(unsigned int bytes) const
   {
-    unsigned int align = this->stub_align();
+    unsigned int align = param_plt_align<size>();
     return (bytes + align - 1) & -align;
   }
 
@@ -4926,9 +4933,7 @@ class Output_data_glink : public Output_section_data
   unsigned int
   global_entry_align(unsigned int off) const
   {
-    unsigned int align = 1 << parameters->options().plt_align();
-    if (!parameters->options().user_set_plt_align())
-      align = size == 64 ? 32 : 4;
+    unsigned int align = param_plt_align<size>();
     return (off + align - 1) & -align;
   }
 
diff --git a/ld/emultempl/ppc32elf.em b/ld/emultempl/ppc32elf.em
index 4e71a78..3007fb2 100644
--- a/ld/emultempl/ppc32elf.em
+++ b/ld/emultempl/ppc32elf.em
@@ -271,7 +271,7 @@ if test -z "$VXWORKS_BASE_EM_FILE" ; then
   { "bss-plt", no_argument, NULL, OPTION_OLD_PLT },
   { "speculate-indirect-jumps", no_argument, NULL, OPTION_SPECULATE_INDIRECT_JUMPS },
   { "no-speculate-indirect-jumps", no_argument, NULL, OPTION_NO_SPECULATE_INDIRECT_JUMPS },
-  { "plt-align", no_argument, NULL, OPTION_PLT_ALIGN },
+  { "plt-align", optional_argument, NULL, OPTION_PLT_ALIGN },
   { "no-plt-align", no_argument, NULL, OPTION_NO_PLT_ALIGN },
   { "sdata-got", no_argument, NULL, OPTION_OLD_GOT },'
 fi
@@ -369,7 +369,16 @@ PARSE_AND_LIST_ARGS_CASES=${PARSE_AND_LIST_ARGS_CASES}'
       break;
 
     case OPTION_PLT_ALIGN:
-      params.plt_stub_align = 5;
+      if (optarg != NULL)
+	{
+	  char *end;
+	  unsigned long val = strtoul (optarg, &end, 0);
+	  if (*end || val > 5)
+	    einfo (_("%P%F: invalid --plt-align `%s'\''\n"), optarg);
+	  params.plt_stub_align = val;
+	}
+      else
+	params.plt_stub_align = 5;
       break;
 
     case OPTION_NO_PLT_ALIGN:
diff --git a/ld/emultempl/ppc64elf.em b/ld/emultempl/ppc64elf.em
index c7c27b0..0baa424 100644
--- a/ld/emultempl/ppc64elf.em
+++ b/ld/emultempl/ppc64elf.em
@@ -872,8 +872,8 @@ PARSE_AND_LIST_ARGS_CASES=${PARSE_AND_LIST_ARGS_CASES}'
       if (optarg != NULL)
 	{
 	  char *end;
-	  unsigned long val = strtoul (optarg, &end, 0);
-	  if (*end || val > 8)
+	  long val = strtol (optarg, &end, 0);
+	  if (*end || (unsigned long) val + 8 > 16)
 	    einfo (_("%P%F: invalid --plt-align `%s'\''\n"), optarg);
 	  params.plt_stub_align = val;
 	}

-- 
Alan Modra
Australia Development Lab, IBM